The UK's four biggest supermarket chains are all cutting up to 2p off a litre of petrol as another fuel price war gets under way.

Unleaded fuel from Asda, Tesco, Sainsbury's and Morrisons will be cheaper from tomorrow morning.

But the price of diesel will remain the same at all four chains' forecourts.

Asda, which was the first to announce a cut, says wholesale petrol prices — what it pays to buy the fuel it sells to motorists — have dropped, allowing it to reduce pump prices. It adds that whoelsale diesel prices have not fallen.

Meanwhile, Tesco says: "As Britain’s biggest petrol retailer, more motorists will make savings at the pumps at Tesco than at any other fuel retailer.”

Morrisons says it was offering "the best value we possibly can" for motorists, while Sainsbury's says: "We're always looking for ways to help our customers save money, particularly as we head towards the festive season."

Drivers filling up at any Asda forecourt will pay no more than 133.7p per litre of unleaded from tomorrow, with diesel buyers charged 139.7p per litre. Other supermarkets' prices are set locally.

The reductions do not necessarily mean any of the supermarkets will be the cheapest fuel provider. The website lists the cheapest in your area.

The site reports average petrol prices on Monday were 138.76p per litre, while the average diesel cost was 143.72p per litre.